PlanSnapper
How it worksPricingGuideLearnToolsSign in
Home / Learn / How to Find or Look Up the Square Footage of a House Online (by Address)

Appraisal Practice · 5 min read

Part of: How to Measure Square Footage: The Complete Guide

How to Find or Look Up the Square Footage of a House Online (by Address)

Public records, MLS data, and real estate portals each report square footage from different sources, and they regularly disagree. Before going on-site, cross-referencing these sources helps establish what the assessor has on file, flag discrepancies, and anticipate where the prior square footage may be wrong. Here is how to read each source and what to do when they conflict.

Get the accurate square footage of your home

Upload a floor plan and get a calculated GLA in minutes. $9 day pass for instant access.

Try PlanSnapper

Where Can I Look Up the Square Footage of a House by Address?

To look up the square footage of any house by address, there are four primary sources, ranked from most accessible to most accurate: the county assessor's online property records, MLS data on Zillow or Redfin, a prior appraisal report, and a floor plan measured by an appraiser. Each one accepts a property address as the lookup key, and each will return a different number. Here is where to find each source and how to interpret the result.

Jump to: Method 1, Method 2, Method 3, Method 4.

Method 1: Look Up Square Footage by Address in County Assessor Records (Most Reliable Free Source)

The county assessor's property database is the primary public record for square footage and accepts a property address as the lookup key. Search "[county name] assessor property search" or "[county name] parcel search" by address to find the relevant portal for the subject property's jurisdiction.

The assessor record typically shows the recorded square footage, building area, year built, and in some cases a breakdown by level. This figure is useful as a baseline. It represents what the jurisdiction has on file and what property tax assessments are based on.

Key limitation: assessor data is often based on permits or exterior estimates taken at time of construction or last major update. It may not reflect additions, conversions, or corrections made since. If the assessor figure looks wrong, see what to do when county assessor square footage is incorrect. Assessors may also use interior measurement or their own GBA methodology rather than the exterior-based ANSI Z765 standard appraisers use, which produces systematically different results. The assessor figure is a starting point for research, not a substitute for field measurement from the exterior.

Method 2: MLS, Zillow, and Redfin

MLS-sourced square footage on Zillow, Redfin, and Realtor.com traces back to one of two places: the county assessor record, or what the listing agent entered when the property was last listed. In most cases it is the assessor record, copied without verification. This means the property square footage records you see on Zillow or Redfin are usually a mirror of the underlying assessor data, not an independent measurement.

When reviewing these figures pre-inspection, the more useful data point is whether the portal's figure matches the assessor record. A material discrepancy (say, Redfin showing 2,400 sq ft against an assessor record of 1,900 sq ft) is often a signal that the listing agent included finished basement area or an addition that the assessor hasn't yet recorded. MLS square footage errors are common and can persist for years without correction. Both scenarios warrant closer review on-site.

See also: How accurate is Zillow square footage?

Method 3: Prior Appraisal Report

A prior appraisal report, if available in the workfile, seller disclosures, or through the lender, contains the most reliable square footage figure available without new field measurement. The GLA from a prior ANSI Z765-compliant appraisal is directly comparable to what a current appraisal will produce, assuming no changes to the structure since that date.

The sketch addendum is the key document: it shows exterior dimensions, floor-by-floor area calculations, and any deductions for stairwell voids or non-GLA areas. Comparing the prior sketch against the current assessor record quickly surfaces additions, discrepancies, or errors that need to be resolved during the inspection.

Method 4: Upload a Floor Plan to PlanSnapper (Most Accurate)

When a floor plan with dimensions is available, whether from a prior appraisal sketch, builder plans, county records, or a listing service like CubiCasa or Matterport, PlanSnapper calculates GLA directly from those dimensions using the same exterior-perimeter methodology appraisers use. Upload the plan, trace the perimeter, set a scale reference from one known dimension, and get a calculated area in about 2 minutes. If you don't have a floor plan yet, see how to get a floor plan of an existing home.

This is useful for pre-inspection due diligence: you can verify whether the listed square footage is plausible before going on-site, and identify any floors or areas that need closer attention during field measurement.

Try PlanSnapper

Why the Numbers Often Don't Match

Assessor records, MLS listings, and appraisal reports can all differ, sometimes by hundreds of square feet, without any of them being incorrect by their own methodology. The discrepancy is usually definitional. See the full breakdown of square footage discrepancies in real estate for how to interpret and resolve them.

ANSI Z765 defines GLA as above-grade, finished, heated area measured from the exterior. Assessors may use interior measurement, different inclusion rules, or building permit data. MLS figures entered by agents may include below-grade finished area, garages, or unheated spaces. A finished basement showing up in one source and not another accounts for the majority of large discrepancies.

Basements are excluded from GLA under ANSI Z765 regardless of finish level. They are reported separately as below-grade finished area. Garages are always excluded. These two categories are the most common source of the gap between what public records show and what an appraiser will report. See: Are basements included in square footage?

Frequently Asked Questions

Where can I find the square footage of my house online?

The fastest free source is your county assessor's online property database. Search "[your county] assessor property search" and look up the parcel by address. The square footage on file there is what most public records, MLS listings, and tax documents are based on. For a more accurate number, a prior appraisal report or a floor plan measured to ANSI Z765 will be more reliable.

How do I look up the square footage of a house by address?

Enter the property address into the county assessor's parcel search, then look for "building area," "living area," or "GLA" on the parcel detail page. Zillow, Redfin, and Realtor.com also accept an address and will display a square footage figure, but in most cases that figure is just a copy of the assessor record.

Are property square footage records public?

Yes. County assessor records, including building square footage, are public records in every U.S. state and are searchable for free by address through the county's online portal. Some counties also publish historical permit data that can be used to verify additions or finished basements.

Is there a free way to find the square footage of a house online?

Yes. County assessor portals are free and accept address searches. Zillow, Redfin, and Realtor.com are also free, though their numbers usually mirror the assessor's record. For a free measured calculation from a floor plan you already have, you can use a free floor plan square footage calculator.

Why does the square footage of my house show different numbers in different places?

Assessor records, MLS listings, and appraisals each measure square footage differently and pull from different source documents. The assessor may use Gross Building Area, MLS may copy from the last listing, and an appraiser uses ANSI Z765 Gross Living Area. The differences are usually definitional, not errors.

Once you have the square footage, you can compare your home to common house sizes (1,500, 2,000, 2,500, or 3,000 sq ft) to put the number in context.

Built for appraisers who need defensible GLA

Upload a floor plan, trace the perimeter, and get a calculated GLA in minutes. ANSI Z765 methodology. No software to install, works in any browser.

Try PlanSnapper

Related Reading

More guides on measuring square footage:

← Back to: How to Measure Square Footage: The Complete Guide